# std::valarray

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< cpp‎ | numeric

Defined in header `<valarray>` |  |
template< class T > class valarray; |  |

`std::valarray` is the class for representing and manipulating arrays of values. It supports element-wise mathematical operations and various forms of generalized subscript operators, slicing and indirect access.

### Notes

`std::valarray` and helper classes are defined to be free of certain forms of aliasing, thus allowing operations on these classes to be optimized similar to the effect of the keyword `restrict` in the C programming language. In addition, functions and operators that take `valarray` arguments are allowed to return proxy objects to make it possible for the compiler to optimize an expression such as v1 = a * v2 + v3; as a single loop that executes v1[i] = a * v2[i] + v3[i]; avoiding any temporaries or multiple passes. However, expression templates make the same optimization technique available for any C++ container, and the majority of numeric libraries prefer expression templates to valarrays for flexibility. Some C++ standard library implementations use expression templates to implement efficient operations on `std::valarray` (e.g. GNU libstdc++ and LLVM libc++). Only rarely are valarrays optimized any further, as in e.g. Intel Integrated Performance Primitives.

### Template parameters

T | - | the type of the elements. The type must meet the NumericType requirements

### Member types

Member type | Definition
`value_type` | `T`

### Member functions

(constructor) | constructs new numeric array (public member function)
(destructor) | destructs the numeric array (public member function)
operator= | assigns the contents (public member function)
operator[] | get/set valarray element, slice, or mask (public member function)
operator+operator-operator~operator! | applies a unary arithmetic operator to each element of the valarray (public member function)
operator+=operator-=operator*=operator/=operator%=operator&=operator|=operator^=operator<<=operator>>= | applies compound assignment operator to each element of the valarray (public member function)
swap | swaps with another valarray (public member function)
size | returns the size of valarray (public member function)
resize | changes the size of valarray (public member function)
sum | calculates the sum of all elements (public member function)
min | returns the smallest element (public member function)
max | returns the largest element (public member function)
shift | zero-filling shift the elements of the valarray (public member function)
cshift | circular shift of the elements of the valarray (public member function)
apply | applies a function to every element of a valarray (public member function)

### Non-member functions

std::swap(std::valarray) (C++11) | specializes the std::swap algorithm (function template)
std::begin(std::valarray) (C++11) | overloads std::begin (function template)
std::end(std::valarray) (C++11) | specializes std::end (function template)
operator+operator-operator*operator/operator%operator&operator|operator^operator<<operator>>operator&&operator|| | applies binary operators to each element of two valarrays, or a valarray and a value (function template)
operator==operator!=operator<operator<=operator>operator>= | compares two valarrays or a valarray with a value (function template)
abs(std::valarray) | applies the function abs to each element of valarray (function template)
##### Exponential functions
exp(std::valarray) | applies the function std::exp to each element of valarray (function template)
log(std::valarray) | applies the function std::log to each element of valarray (function template)
log10(std::valarray) | applies the function std::log10 to each element of valarray (function template)
##### Power functions
pow(std::valarray) | applies the function std::pow to two valarrays or a valarray and a value (function template)
sqrt(std::valarray) | applies the function std::sqrt to each element of valarray (function template)
##### Trigonometric functions
sin(std::valarray) | applies the function std::sin to each element of valarray (function template)
cos(std::valarray) | applies the function std::cos to each element of valarray (function template)
tan(std::valarray) | applies the function std::tan to each element of valarray (function template)
asin(std::valarray) | applies the function std::asin to each element of valarray (function template)
acos(std::valarray) | applies the function std::acos to each element of valarray (function template)
atan(std::valarray) | applies the function std::atan to each element of valarray (function template)
atan2(std::valarray) | applies the function std::atan2 to a valarray and a value (function template)
##### Hyperbolic functions
sinh(std::valarray) | applies the function std::sinh to each element of valarray (function template)
cosh(std::valarray) | applies the function std::cosh to each element of valarray (function template)
tanh(std::valarray) | applies the function std::tanh to each element of valarray (function template)

### Helper classes

slice | BLAS-like slice of a valarray: starting index, length, stride (class)
slice_array | proxy to a subset of a valarray after applying a slice (class template)
gslice | generalized slice of a valarray: starting index, set of lengths, set of strides (class)
gslice_array | proxy to a subset of a valarray after applying a gslice (class template)
mask_array | proxy to a subset of a valarray after applying a boolean mask `operator[]` (class template)
indirect_array | proxy to a subset of a valarray after applying indirect `operator[]` (class template)

### Deduction guides(since C++17)

### See also

simd (C++26) | convenience alias template for `basic_simd` that can specify its width (alias template)
simd_mask (C++26) | convenience alias template for `basic_simd_mask` that can specify its width (alias template)
simd (parallelism TS v2) | data-parallel vector type (class template)
simd_mask (parallelism TS v2) | data-parallel type with the element type bool (class template)

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